Automatic power transmissions are currently used in a number of passenger vehicles sold within this country. As is well known, the automatic transmission provides a plurality of planetary speed ratios in both the forward direction and at least one reverse speed ratio. These speed ratios are established through the use of a plurality of planetary gearsets, which are controlled by a number of fluid-operated friction torque-transmitting mechanisms, commonly termed clutches and brakes.
It has become a standard to provide at least four forward speed ratios in automatic transmissions for use in passenger vehicles. More recently, automobile manufacturers have increased the forward speed ratios to five and in some instances six. This, of course, requires the addition of planetary gearsets as well as trying to maintain the number of torque-transmitting mechanisms at a minimum.
A number of the currently proposed six-speed planetary transmissions provide three planetary gearsets and five friction torque-transmitting mechanisms. This gives rise to a packaging situation regarding the positioning of the torque-transmitting mechanisms within the transmission environment.
One such transmission is described in U.S. Pat. No. 5,106,352 issued to Lepelletier Apr. 21, 1992. This power transmission provides six forward speed ratios and employs an input gearset and a ratio gearset. The input gearset of Lepelletier has a stationary member in the forward planetary gearset to provide an underdrive input to the ratio gearset, which is preferably a Ravigneaux type set.
U.S. Pat. No. 6,135,912 issued to Tsukamoto, et al. Oct. 24, 2000, provides some solutions for packaging the friction devices within the Lepelletier type of six-speed transmission. However, there are many other six-speed planetary gearsets with five torque-transmitting mechanisms that cannot be accommodated by the Tsukamoto, et al. arrangement.